The specific objectives of this proposal are twofold: 1) Quantitative and qualitative in vitro analysis of the functional activity of T cell subsets (T gamma and T mu) in M.S. patients and controls. The various T cell functions to be studied include: a) suppressor activity; b) helper activity, c) cytotoxic activity and d) antibody dependent cell mediated cytotoxicity. Each activity will be correlated with HLA-Dw/DRw types to determine if any T cell perturbations are specifically associated with HLA-Dw2 or other HLA-Dw region types. 2) Prospective analysis of T cell activity and function in M.S. patients who have been thymectomized. In this part of the study we hope to identify which T cell functions are altered by therapy and if these changes correlate with clinical response. We will also determine if the parameter of T cell function can be utilized to predict which M.S. patients are most likely to benefit from thymectomy.